Matt,

Try

lnMinTrackSizeX = loWas.Long2NumFromBuffer(lParam+24) 
lnMinTrackSizeY = loWas.Long2NumFromBuffer(lParam+28) 
lnMaxTrackSizeX = loWas.Long2NumFromBuffer(lParam+32) 
lnMaxTrackSizeY = loWas.Long2NumFromBuffer(lParam+36) 
...

lnMinTrackSizeX = 200
lnMinTrackSizeY = 200

lnMaxTrackSizeX = 500
lnMaxTrackSizeY = 500

WITH loWas
	lcNewMinMax = 	.Num2Long(lnMinTrackSizeX) + ;
			.Num2Long(lnMinTrackSizeY) + ;
			.Num2Long(lnMaxTrackSizeX) + ;
			.Num2Long(lnMaxTrackSizeY)
ENDWITH 					

* Copy values back to lParam at offset 24
= SYS(2600, lParam+24, 16, lcNewMinMax)

* For testing, retrieve again to verify that they're set correctly
lnMinTrackSizeX = loWas.Long2NumFromBuffer(lParam+24) 
lnMinTrackSizeY = loWas.Long2NumFromBuffer(lParam+28) 
lnMaxTrackSizeX = loWas.Long2NumFromBuffer(lParam+32) 
lnMaxTrackSizeY = loWas.Long2NumFromBuffer(lParam+36) 

>You, my friend, are a wizard. <g> Thank you! That worked like a charm. I should've caught the event bound parameters problem, but I just haven't have to deal with Structures and Pointers enough to be 100% comfortable with them yet.
>
>So if I can trouble you for one more thing, the MS documentation says that you can change the value in the struct, thereby setting the window's min or max size, which is my goal for this. I've got VB reference code below, but I'm more than a little unclear on how to translate it to VFP...
>
<snip>